Benedikt Christopher Spies

Clinical Outcomes of Zirconia Dental Implants: A Systematic Review

To determine the survival rate and marginal bone loss (MBL) of zirconia dental implants restored with single crowns or fixed dental prostheses. An electronic search was conducted up to November 2015 (without any restriction regarding the publication time) through the databases MEDLINE (PubMed), Cochrane Library, and EMBASE to identify randomized controlled clinical trials and prospective clinical trials including >15 patients. Primary outcomes were survival rate and MBL. Furthermore, the influence of several covariates on MBL was evaluated. Qualitative assessment and statistical analyses were performed. This review was conducted according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines for systematic reviews. With the applied search strategy, 4,196 titles could be identified. After a screening procedure, 2 randomized controlled clinical trials and 7 prospective clinical trials remained for analyses. In these trials, a total of 326 patients received 398 implants. The follow-up ranged from 12 to 60 mo. Implant loss was mostly reported within the first year, especially within the healing period. Thereafter, nearly constant survival curves could be observed. Therefore, separate meta-analyses were performed for the first and subsequent years, resulting in an implant survival rate of 95.6% (95% confidence interval: 93.3% to 97.9%) after 12 mo and, thereafter, an expected decrease of 0.05% per year (0.25% after 5 y). Additionally, a meta-analysis was conducted for the mean MBL after 12 mo, resulting in 0.79 mm (95% confidence interval: 0.73 to 0.86 mm). Implant bulk material and design, restoration type, and the application of minor augmentation procedures during surgery, as well as the modes of temporization and loading, had no statistically significant influence on MBL. The short-term cumulative survival rates and the MBL of zirconia implants in the presented systematic review are promising. However, additional data are still needed to confirm the long-term predictability of these implants.

Evaluation of Zirconia‐Based All‐Ceramic Single Crowns and Fixed Dental Prosthesis on Zirconia Implants: 5‐Year Results of a Prospective Cohort Study

Objective The objective of this 5-year cohort investigation was to determine the survival and success rate of all-ceramic reconstructions on zirconia oral implants. Material and Methods Ninety-three patients received 122 one-piece zirconia implants. One hundred seventeen implants were restored with 63 single crowns (SCs) and 27 three-unit bridges (fixed dental prostheses, FDPs) fabricated using zirconia frameworks (Procera® Zirconia, Nobel Biocare®, Goteborg, Sweden) hand-layered with a silicate ceramic (NobelRondo™ Zirconia, Nobel Biocare®). With any occurrence of chipping regarded as an event, Kaplan-Meier success curves were plotted. Covariates (gender, location, manufacturing date) were estimated by the use of log-rank tests. Results Eighty-nine patients received prosthetic reconstructions. Sixty-three of them were seen at the 5-year follow-up, with a mean observation time of 58.2 months (47 patients with SCs, 16 patients with FDPs). Reasons for the decreasing number of patients at the follow-up sessions included dropouts due to implant loss (n = 21), moving (n = 3), missed appointments (n = 1), and severe illness (n = 1). Over half of the SCs (57.2%) and 38% of the FDPs were successful after an observation time of 5 years (overall success rate of 51.7%). The performed log-rank tests revealed no statistically significant differences for the success curves regarding the above-mentioned covariates. Among the 63 restorations that completed the study, 11 of 47 SCs and one of 16 FDPs had to be replaced due to the severity of the observed chipping. This results in survival rates of 76.6% for the SCs and 93.8% for the FDPs. No framework fractures or decementations were observed in any group. Conclusion Hand-layering of zirconia-based SCs and FDPs with NobelRondo™ Zirconia restoring one-piece zirconia implants did not show acceptable survival and success rates. Meanwhile, the material has been recalled from the market. It is advised that new materials should undergo adequate preclinical evaluation before coming to the market.OBJECTIVE The objective of this 5-year cohort investigation was to determine the survival and success rate of all-ceramic reconstructions on zirconia oral implants. MATERIAL AND METHODS Ninety-three patients received 122 one-piece zirconia implants. One hundred seventeen implants were restored with 63 single crowns (SCs) and 27 three-unit bridges (fixed dental prostheses, FDPs) fabricated using zirconia frameworks (Procera(®) Zirconia, Nobel Biocare(®), Göteborg, Sweden) hand-layered with a silicate ceramic (NobelRondo(™) Zirconia, Nobel Biocare(®)). With any occurrence of chipping regarded as an event, Kaplan-Meier success curves were plotted. Covariates (gender, location, manufacturing date) were estimated by the use of log-rank tests. RESULTS Eighty-nine patients received prosthetic reconstructions. Sixty-three of them were seen at the 5-year follow-up, with a mean observation time of 58.2 months (47 patients with SCs, 16 patients with FDPs). Reasons for the decreasing number of patients at the follow-up sessions included dropouts due to implant loss (n = 21), moving (n = 3), missed appointments (n = 1), and severe illness (n = 1). Over half of the SCs (57.2%) and 38% of the FDPs were successful after an observation time of 5 years (overall success rate of 51.7%). The performed log-rank tests revealed no statistically significant differences for the success curves regarding the above-mentioned covariates. Among the 63 restorations that completed the study, 11 of 47 SCs and one of 16 FDPs had to be replaced due to the severity of the observed chipping. This results in survival rates of 76.6% for the SCs and 93.8% for the FDPs. No framework fractures or decementations were observed in any group. CONCLUSION Hand-layering of zirconia-based SCs and FDPs with NobelRondo(™) Zirconia restoring one-piece zirconia implants did not show acceptable survival and success rates. Meanwhile, the material has been recalled from the market. It is advised that new materials should undergo adequate preclinical evaluation before coming to the market.

Alumina reinforced zirconia implants: Effects of cyclic loading and abutment modification on fracture resistance

OBJECTIVE The aim of the study was to evaluate the thermomechanical behavior of alumina-toughened zirconia (ATZ) oral implants in the artificial mouth and the fracture resistance (fracture load and bending moment) in a subsequent static fracture load test. The effects of abutment modification and different cyclic loadings were evaluated. METHODS A total of 48 implants were used. 24 implants were left as machined (Group A), and 24 implants were shape modified at the abutment (Group B). Groups were divided into three subgroups composed of 8 samples each (A1/B1: no cyclic loading; A2/B2: 1.2 million cycles; A3/B3: 5 million cycles). Subsequently, all implants were statically loaded to the point of fracture. RESULTS The implants showed the following survival rates after the artificial mouth: A2 and B2 100%; A3 and B3 87.5%. The following average fracture resistance values were found (fracture load [N]/bending moment [Nmm]): A1 (583/2907), B1 (516/2825), A2 (618/2737), B2 (550/3150), A3 (802/3784) and B3 (722/3809). After 5 million loading cycles a significant increase in fracture load and bending moment was found. Modification of the abutment significantly decreased the fracture load of implants without foregoing dynamic loading. However, the shape modification altered the lever arm. For that reason, a smaller load resulted in the same bending moment. Therefore, abutment modification had no significant influence on the fracture resistance of ATZ. SIGNIFICANCE Neither thermomechanical cycling in an aqueous environment nor modification of the abutment had a negative effect on the fracture resistance of ATZ.

Alumina reinforced zirconia implants: 1-year results from a prospective cohort investigation

OBJECTIVE The objective of this investigation was to determine the clinical and radiographic outcome of a one-piece alumina-toughened zirconia (ATZ) oral implant for single tooth replacement after 1 year. MATERIALS AND METHODS A total of 27 patients received one ATZ implant each in a one-stage implant surgery with immediate temporization. Standardized radiographs were taken at implant insertion and after 1 year to monitor peri-implant bone loss. Several soft tissue parameters were evaluated at prosthesis insertion and at the 1-year follow-up. RESULTS Three patients did not receive a prosthetic reconstruction due to implant loss during the healing period. As a result, 24 patients were seen at the 1-year follow-up, giving a cumulative survival rate of 88.9%. The average marginal bone loss after 1 year was 0.77 mm. Only two implants (8.3%) lost at least 2 mm bone, whereas none of the implants lost more than 3 mm. Probing depth and clinical attachment level increased over 1 year at the implant sites, whereas gingival recession remained stable. Mombellis bleeding and plaque indices showed no statistically significant change within the first year. CONCLUSION Owing to a total of 27 inserted implants, three failures within the first 4 months after implant placement carry weight. Therefore, the cumulative survival rate of the presented ceramic implant was slightly below reported survival rates of titanium implants when immediately restored. The recorded radiographic bone loss and peri-implant soft tissue parameters showed promising short-term results. The presented ATZ implant seems to be a candidate for clinical usage.

Clinical and Patient-reported Outcomes of a Zirconia Oral Implant: Three-year Results of a Prospective Cohort Investigation

The objective of this study was to determine the clinical, radiographic, and patient-reported outcomes of a 1-piece alumina-toughened zirconia implant restored with single crowns (SCs) or 3-unit fixed dental prostheses (FDPs) after 3 y of observation. Forty patients received 53 implants, placed in a 1-stage operation with immediate temporization. Finally, 50 implants were restored with 24 SCs and 13 FDPs. To evaluate peri-implant bone loss, standardized radiographs were taken at implant insertion, at final restoration delivery, and after 1 and 3 y. Additionally, several soft tissue parameters and patient-reported outcome measures were evaluated. Linear mixed models with random intercept for each patient and patients as clusters were used to compare subgroups. Three patients did not receive a SC due to early implant loss, and 1 patient died. As a result, 36 patients with 49 implants were followed-up for 3 y, giving a cumulative survival rate of 94.2%. The average marginal bone loss amounted to 0.79 mm (SCs, 0.47 mm; FDPs, 1.07 mm; P < 0.001). After the delivery of the final prosthetic restoration, further bone loss was not statistically significant (0.09 mm; P = 0.700). Probing depth, clinical attachment level, and modified bleeding index increased significantly at the implant sites, whereas gingival recession decreased significantly. Compared with the pretreatment questionnaires, the patient-reported outcome measures showed a permanently improved perception of function, aesthetics, sense, speech and self-esteem. The survival rate of the investigated ceramic implant system seems to be comparable to reported survival rates of titanium implants when immediately restored. The recorded parameters suggest its potential for clinical utilization.

Two-piece zirconia oral implants withstand masticatory loads: An investigation in the artificial mouth.

OBJECTIVE To evaluate the fracture resistance of two-piece zirconia oral implants after long-term thermomechanical cycling in an aqueous environment. Non-loaded samples and a one-piece implant system served as control groups. METHODS A total of 48 zirconia implants were evaluated: 16 one-piece implants (ATZ; Group A) and 32 differently connected two-piece implants (16 screwed, Group B; 16 bonded, Group C) made of Y-TZP-A (implant+abutment; B) and Y-TZP-A/ATZ (implant/abutment; C), respectively. These groups were divided into two subgroups composed of 8 samples. The samples of subgroups 1 (A1, B1, C1) were not exposed to any cyclic loading, whereas subgroups 2 (A2, B2, C2) were loaded with 10 million cycles (98 N). Subsequently, all 48 implants were statically loaded to fracture. RESULTS A constant load on distinct lever arms resulted in different exerted bending moments during the dynamic loading (A2: 23.4Ncm, B2: 17.9 Ncm, C2: 32.3 Ncm). All implants survived the long-term thermomechanical cycling. For the static loading the following average bending moments were calculated: A1/A2: 362/399 Ncm; B1/B2: 398/346 Ncm; C1/C2: 380/252 Ncm. Foregoing dynamic loading significantly increased fracture resistance of Group A implants, whereas Group B/C implants showed significantly decreased values. Potentially owed to the experimental setup in an aqueous environment of 60 °C, 5/8 C2 samples showed mobility between implant and abutment due to debonding after dynamic loading conditions. SIGNIFICANCE The evaluated ceramic implant systems seem to be able to resist physiological chewing forces long-term. Within the limitations of the experimental setup, the connecting mechanism of Group C implants might be a weak point.

CAD/CAM-fabricated implant-supported restorations: a systematic review

OBJECTIVES The aim of this systematic review was to identify and summarize the available literature related to CAD/CAM-fabricated implant-supported restorations. MATERIALS AND METHODS A systematic review of the literature was conducted using the Cochrane Library and the US Library of Medicine, National Institute of Health databases (Pubmed). Several search runs with specific search terms were performed and combined. All published papers available on the databases up to January 15, 2015 were considered with primarily no restrictions. RESULTS About 12 of 3484 identified papers met the inclusion criteria and were analyzed in the present review. One paper reported results on implant-supported single crowns (SCs), one on partial fixed dental prostheses (FDPs), and 10 papers reported results on full-arch screw-retained FDPs. Publications on SCs and FDPs were very limited but it was possible to identify 10 papers reporting adequate results on full-arch screw-retained FDPs. Survival rates ranged between 92% and 100% with observation times of 1-10 years. CONCLUSION The available data provided promising results for CAD/CAM-fabricated implant-supported restorations; nonetheless, current evidence is limited due to the quality of available studies and the paucity of data on long-term clinical outcomes of 5 years or more. In the sense of an evidence-based dentistry, the authors recommend further studies designed as randomized controlled clinical trials and reported according to the CONSORT statement.

Fatigue induced changes in conical implant–abutment connections

OBJECTIVES Based on the current lack of data and understanding of the wear behavior of dental two-piece implants, this study aims for evaluating the microgap formation and wear pattern of different implants in the course of cyclic loading. METHODS Several implant systems with different conical implant-abutment interfaces were purchased. The implants were first evaluated using synchrotron X-ray high-resolution radiography (SRX) and scanning electron microscopy (SEM). The implant-abutment assemblies were then subjected to cyclic loading at 98N and their microgap was evaluated after 100,000, 200,000 and 1 million cycles using SRX, synchrotron micro-tomography (μCT). Wear mechanisms of the implant-abutment connection (IAC) after 200,000 cycles and 1 million cycles were further characterized using SEM. RESULTS All implants exhibit a microgap between the implant and abutment prior to loading. The gap size increased with cyclic loading with its changes being significantly higher within the first 200,000 cycles. Wear was seen in all implants regardless of their interface design. The wear pattern comprised adhesive wear and fretting. Wear behavior changed when a different mounting medium was used (brass vs. polymer). SIGNIFICANCE A micromotion of the abutment during cyclic loading can induce wear and wear particles in conical dental implant systems. This feature accompanied with the formation of a microgap at the IAC is highly relevant for the longevity of the implants.

CAD/CAM-fabricated ceramic implant-supported single crowns made from lithium disilicate: Final results of a 5-year prospective cohort study

BACKGROUND All-ceramic bilayer systems suffer from technique-sensitivity, resulting in increased technical complication rates. This might be overcome by monolithic reconstructions, facilitating digital workflows. PURPOSE To evaluate the clinical and patient-reported outcome of CAD/CAM-fabricated implant-supported single crowns (ISCs) made of lithium disilicate (LS2 ) cemented on ceramic implants 5 years after implant installation. MATERIALS AND METHODS Twenty-four patients were included in the study. All participants received a one-piece ceramic implant in anterior (4 incisors) and posterior regions (10 premolars, 10 molars). LS2 crowns were computer-aided designed (CAD), manufactured (CAM) and adhesively luted onto the implants. Follow-ups were performed yearly up to 60 months after implant installation. The survival/success rates of the restorations were calculated according to modified US Public Health Service criteria as follows: Clinically relevant defects that could be repaired intraorally were accepted for survival, whereas small-area chippings, roughness (ø < 2 mm), slightly soundable marginal gaps, minimal undercontours/overcontours, and tolerable color deviations were accepted for success. Kaplan-Meier plots were used for the success/survival analyses. Furthermore, patient-reported outcome measures (PROMs) were assessed by applying visual analog scales (VAS). Linear (PROMs) and logistic (USPHS criteria) mixed models were fitted to evaluate time effects on response variables. RESULTS Twenty-two ISCs could be evaluated 55.2 ± 4.2 months after prosthetic delivery. Two patients were reported as drop-outs (1 died, 1 moved abroad). No failures were observed, resulting in 100% survival. At two ISCs, a major-roughness had to be treated. This resulted in a Kaplan-Meier success estimate of 91.7% (95%CI: 70.6%-97.9%). Compared with pretreatment, all surveys at prosthetic delivery except for self-esteem (P = .375) showed significantly improved VAS scores. No decrease in satisfaction could be observed over time until the end of follow-up (P ≥ .056). CONCLUSION Concerning survival/success rates and PROMs, the evaluated crown-implant system showed favorable mid-term results. To date, there are no comparable data available for implant-supported ISCs made of LS2 .

Peri-implant bone response to retrieved human zirconia oral implants after a 4-year loading period: A histologic and histomorphometric evaluation of 22 cases.

AIM To evaluate the bone tissue response to surface modified zirconia oral implants retrieved from humans. MATERIALS AND METHODS Twenty-nine one-piece zirconia implants showed increased marginal bone loss and did not response to the applied peri-implantitis therapy. After their removal using a trephine bur, 22 of the implant-bone biopsies were suitable for an evaluation and immediately immersed in formalin for two weeks. Subsequent, the retrieved specimens were histologically prepared and the regions still showing osseointegration computer-assisted analyzed regarding the bone-to-implant contact (BIC) and bone density using a transmitted-light microscope. RESULTS The removed implants were in situ for a mean time period of 47.7 months. After their removal, compact bone could be depicted at the apical regions. The remaining bone that was attached to the implants contained a regular lamellar structure with osteons and osteocytes. The BIC ranged from 58.1% to 93.7% (mean: 76.5%) and the bone area/density within the implant threads ranged from 57% to 97.2% (mean: 84.8%). CONCLUSIONS The porous zirconia implants showed a sufficient BIC in the areas where bone still was attached. Although the implants had to be removed due to increased bone loss, it seems that the presented zirconia implant surface per se elicited appropriate osseointegration.